Algorithmically and seamlessly weaving undisclosed advertising (or other editorial content) into conversational output is their holy grail. It's the endgame. There's a reason they're pushing so hard.
I'd even walk back on just calling it advertising, because we immediately think of the usual ads we see everywhere. The actual thing here might be much more subtle and worrying, you could call it undisclosed influence.
Probably endgame plus getting "too big to fail" and getting gov't bailouts if things don't work out. It's part of the lobbying theme that LLMs are the next great power struggle.